WASHINGTON — President Trump placed a wreath at the Tomb of the Unknowns at a Memorial Day ceremony at Arlington National Cemetery Monday and expressed the nation’s “boundless and undying” gratitude to Americans who have fallen in battle and to the families they left behind.

The playing of “Taps” echoed as Trump placed the wreath and then covered his heart with his hand as military officers saluted.

In his remarks, he told the stories of two soldiers who died in Afghanistan, Green Beret Capt. Andrew D. Byers of Colorado Springs and Christopher D. Horton of the Oklahoma National Guard. He also hailed Bob Dole, the former senator who suffered lifelong injuries in World War II and attended Monday’s ceremony.

President Trump listens as “Taps” is played during a wreath laying ceremony at Arlington National Cemetery.

And Trump singled out his homeland security secretary, John Kelly, for whom military sacrifice is close to home.

Kelly led the U.S. Southern Command and lost his son, Robert Kelly, who stepped on a land mine on a Marine patrol in Afghanistan. John Kelly’s other son, Johnny, is preparing for his fifth military deployment. And Kelly’s son-in-law Jake is a wounded warrior.

Earlier Monday, Trump posted two tweets thanking the men and women who died in service to the United States.

In the first, he said: “Today we remember the men and women who made the ultimate sacrifice in serving. Thank you, God bless your families & God bless the USA!”

In the second, he said: “I look forward to paying my respects to our brave men and women on this Memorial Day at Arlington National Cemetery later this morning.”